San Joaquin County Water Quality: 7 Cities Ranked by the Records
San Joaquin County, California: 7 city reports built from EPA and utility records. A county has many suppliers; each city shows the system that serves it.
Highest result for each contaminant
One row per contaminant: the highest result any system in the county reported, against its limit. Open a row for the systems behind it.
Perfluorooctanesulfonic acid (PFOS)Detected in 5 systems of 7 tested4.0 ng/L federal MCL (2024) · US EPAHighest28 ng/L
- CITY OF STOCKTON28 ng/LSample date: 2023-02-28 to 2025-12-02
- CITY OF LATHROP17 ng/LSample date: 2024-01-16 to 2024-10-14
- RIPON, CITY OF12 ng/LSample date: 2024-07-31 to 2025-01-14
- LODI, CITY OF5.6 ng/LSample date: 2023-11-13 to 2025-07-28
- CALIFORNIA WATER SERVICE - STOCKTON5.2 ng/LSample date: 2025-01-06 to 2026-03-10
- MANTECA, CITY OFNot detected · below 4.0 ng/L lab reporting limitSample date: 2025-01-15 to 2025-10-21
- TRACY, CITY OFNot detected · below 4.0 ng/L lab reporting limitSample date: 2024-01-25 to 2025-04-09
LithiumDetected in 2 systems of 7 tested10 µg/L EPA health reference level (screening, not a legal limit) · US EPAHighest28.5 µg/L
- TRACY, CITY OF28.5 µg/LSample date: 2024-01-25 to 2025-04-09
- RIPON, CITY OF9.93 µg/LSample date: 2024-07-31 to 2025-01-14
- CALIFORNIA WATER SERVICE - STOCKTONNot detected · below 9.0 µg/L lab reporting limitSample date: 2025-01-06 to 2026-03-10
- CITY OF LATHROPNot detected · below 9.0 µg/L lab reporting limitSample date: 2024-01-16 to 2024-10-14
- CITY OF STOCKTONNot detected · below 9.0 µg/L lab reporting limitSample date: 2023-02-28 to 2025-12-02
- LODI, CITY OFNot detected · below 9.0 µg/L lab reporting limitSample date: 2023-11-13 to 2025-07-28
- MANTECA, CITY OFNot detected · below 9.0 µg/L lab reporting limitSample date: 2025-01-15 to 2025-10-21
Perfluorohexanesulfonic acid (PFHxS)Detected in 4 systems of 7 tested10 ng/L federal MCL (2024) · US EPAHighest19 ng/L
- MANTECA, CITY OF19 ng/LSample date: 2025-01-15 to 2025-10-21
- LODI, CITY OF6.1 ng/LSample date: 2023-11-13 to 2025-07-28
- CITY OF LATHROP3.5 ng/LSample date: 2024-01-16 to 2024-10-14
- RIPON, CITY OF3.5 ng/LSample date: 2024-07-31 to 2025-01-14
- CALIFORNIA WATER SERVICE - STOCKTONNot detected · below 3.0 ng/L lab reporting limitSample date: 2025-01-06 to 2026-03-10
- CITY OF STOCKTONNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-02-28 to 2025-12-02
- TRACY, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-01-25 to 2025-04-09
Perfluorooctanoic acid (PFOA)Detected in 4 systems of 7 tested4.0 ng/L federal MCL (2024) · US EPAHighest7 ng/L
- MANTECA, CITY OF7 ng/LSample date: 2025-01-15 to 2025-10-21
- CITY OF STOCKTON6.7 ng/LSample date: 2023-02-28 to 2025-12-02
- LODI, CITY OF6.2 ng/LSample date: 2023-11-13 to 2025-07-28
- RIPON, CITY OF5.2 ng/LSample date: 2024-07-31 to 2025-01-14
- CALIFORNIA WATER SERVICE - STOCKTONNot detected · below 4.0 ng/L lab reporting limitSample date: 2025-01-06 to 2026-03-10
- CITY OF LATHROPNot detected · below 4.0 ng/L lab reporting limitSample date: 2024-01-16 to 2024-10-14
- TRACY, CITY OFNot detected · below 4.0 ng/L lab reporting limitSample date: 2024-01-25 to 2025-04-09
Water hardnessDetected in 1 systemAesthetic, no federal health limit · USGSHighest8.6 gpg
- CITY OF STOCKTON8.6 gpgReporting year: 2025
Lead (90th percentile)Detected in 1 system of 7 tested15 µg/L federal action level · US EPAHighest0.4 µg/L
- MANTECA, CITY OF0.4 µg/LMonitoring period: 2022–2024
- CALIFORNIA WATER SERVICE - STOCKTONNot detectedMonitoring period: 2022–2024
- CITY OF LATHROPNot detectedMonitoring period: 2022–2024
- CITY OF STOCKTONNot detectedMonitoring period: 2025–2027 (still open)
- LODI, CITY OFNot detectedMonitoring period: 2022–2024
- RIPON, CITY OFNot detectedMonitoring period: 2024–2026 (still open)
- TRACY, CITY OFNot detectedMonitoring period: 2022–2024
Perfluorobutanesulfonic acid (PFBS)Detected in 4 systems of 7 tested2,000 ng/L EPA health advisory (screening, not a legal limit) · US EPAHighest17 ng/L
- LODI, CITY OF17 ng/LSample date: 2023-11-13 to 2025-07-28
- CITY OF STOCKTON6.2 ng/LSample date: 2023-02-28 to 2025-12-02
- CITY OF LATHROP5 ng/LSample date: 2024-01-16 to 2024-10-14
- MANTECA, CITY OF3.9 ng/LSample date: 2025-01-15 to 2025-10-21
- CALIFORNIA WATER SERVICE - STOCKTONNot detected · below 3.0 ng/L lab reporting limitSample date: 2025-01-06 to 2026-03-10
- RIPON, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-07-31 to 2025-01-14
- TRACY, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-01-25 to 2025-04-09
Perfluorohexanoic acid (PFHxA)Detected in 2 systems of 7 tested400,000 ng/L Michigan EGLE state MCL (strictest US state) · Michigan EGLEHighest9.5 ng/L
- MANTECA, CITY OF9.5 ng/LSample date: 2025-01-15 to 2025-10-21
- LODI, CITY OF5 ng/LSample date: 2023-11-13 to 2025-07-28
- CALIFORNIA WATER SERVICE - STOCKTONNot detected · below 3.0 ng/L lab reporting limitSample date: 2025-01-06 to 2026-03-10
- CITY OF LATHROPNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-01-16 to 2024-10-14
- CITY OF STOCKTONNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-02-28 to 2025-12-02
- RIPON, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-07-31 to 2025-01-14
- TRACY, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-01-25 to 2025-04-09
2 more contaminants detectedShow
Perfluoroheptanoic acid (PFHpA)Detected in 1 system of 7 testedNo federal or state limit; shown for transparencyHighest3.3 ng/L
- LODI, CITY OF3.3 ng/LSample date: 2023-11-13 to 2025-07-28
- CALIFORNIA WATER SERVICE - STOCKTONNot detected · below 3.0 ng/L lab reporting limitSample date: 2025-01-06 to 2026-03-10
- CITY OF LATHROPNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-01-16 to 2024-10-14
- CITY OF STOCKTONNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-02-28 to 2025-12-02
- MANTECA, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2025-01-15 to 2025-10-21
- RIPON, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-07-31 to 2025-01-14
- TRACY, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-01-25 to 2025-04-09
Perfluoropentanoic acid (PFPeA)Detected in 1 system of 7 testedNo federal or state limit; shown for transparencyHighest5.4 ng/L
- LODI, CITY OF5.4 ng/LSample date: 2023-11-13 to 2025-07-28
- CALIFORNIA WATER SERVICE - STOCKTONNot detected · below 3.0 ng/L lab reporting limitSample date: 2025-01-06 to 2026-03-10
- CITY OF LATHROPNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-01-16 to 2024-10-14
- CITY OF STOCKTONNot detected · below 3.0 ng/L lab reporting limitSample date: 2023-02-28 to 2025-12-02
- MANTECA, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2025-01-15 to 2025-10-21
- RIPON, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-07-31 to 2025-01-14
- TRACY, CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-01-25 to 2025-04-09
22 PFAS tested, none detected in any systemShow
Tested in these 7 systems: CALIFORNIA WATER SERVICE - STOCKTON, CITY OF LATHROP, CITY OF STOCKTON, LODI, CITY OF, MANTECA, CITY OF, RIPON, CITY OF, TRACY, CITY OF
- 11-Chloroeicosafluoro-3-oxaundecane-1-sulfonic acid (11Cl-PF3OUdS)
- 1H, 1H, 2H, 2H-perfluorodecane sulfonic acid (8:2 FTS)
- 1H, 1H, 2H, 2H-perfluorohexane sulfonic acid (4:2 FTS)
- 1H, 1H, 2H, 2H-perfluorooctane sulfonic acid (6:2 FTS)
- 4,8-Dioxa-3H-perfluorononanoic acid (ADONA)
- 9-Chlorohexadecafluoro-3-oxanone-1-sulfonic acid (9Cl-PF3ONS)
- Hexafluoropropylene oxide dimer acid (HFPO-DA) (GenX chemicals)
- N-ethyl perfluorooctanesulfonamidoacetic acid (NEtFOSAA)
- N-methyl perfluorooctanesulfonamidoacetic acid (NMeFOSAA)
- Nonafluoro-3,6-dioxaheptanoic acid (NFDHA)
- Perfluoro (2-ethoxyethane) sulfonic acid (PFEESA)
- Perfluoro-3-methoxypropanoic acid (PFMPA)
- Perfluoro-4-methoxybutanoic acid (PFMBA)
- Perfluorobutanoic acid (PFBA)
- Perfluorodecanoic acid (PFDA)
- Perfluorododecanoic acid (PFDoA)
- Perfluoroheptanesulfonic acid (PFHpS)
- Perfluorononanoic acid (PFNA)
- Perfluoropentanesulfonic acid (PFPeS)
- Perfluorotetradecanoic acid (PFTA)
- Perfluorotridecanoic acid (PFTrDA)
- Perfluoroundecanoic acid (PFUnA)
Cities ranked by the records
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Ranked by the Purity Score of each city's main water system, highest first. Scores belong to water systems; there is no county score. The score is computed only from contaminants measured in the published EPA record, so this ranks the record, not which city's water is safest. How the score works.
0of 7 cities above the 15 µg/L action level
Based on each system's 90th-percentile result. Lead from household plumbing isn't in this record.
Lead in California1city reports hardness · Stockton, 8.6 gpg
Hard on the USGS scale. An aesthetic measure with no federal health limit.
Hard water explainedLargest water systems
- StocktonCITY OF STOCKTON · CA3910012192,702 served
- Garden AcresCALIFORNIA WATER SERVICE - STOCKTON · CA3910001182,775 served
- TracyTRACY, CITY OF · CA391001198,215 served
- MantecaMANTECA, CITY OF · CA391000584,928 served
- LodiLODI, CITY OF · CA391000467,093 served
- LathropCITY OF LATHROP · CA391001538,596 served
- RiponRIPON, CITY OF · CA391000715,753 served
Frequently asked
How does San Joaquin County tap water compare across cities?
PurityMap ranks 7 cities in San Joaquin County by the Purity Score of each city's main water system, computed only from contaminants measured in the published EPA record. Scores belong to water systems, not to cities. The highest published score is Tracy's main water system: TRACY, CITY OF · PWSID CA3910011 · Purity Score 100 (Excellent) · Confidence: moderate · Assessed at the water-system level. The ranking compares the records, not which city's water is safest, and your own tap can differ with household plumbing.
How many San Joaquin County cities had a PFAS sample above a 2024 EPA limit?
6 of 7 San Joaquin County city reports had a PFAS sample above a 2024 EPA limit in EPA's UCMR 5 testing, including Stockton (PFOS 28 ng/L), Lathrop (PFOS 17 ng/L), Ripon (PFOS 12 ng/L). That limit is judged on a yearly average, and water systems have until 2029 to meet it, so a single sample is not a violation. PFAS were detected at any level in 6.
Is there lead in San Joaquin County tap water?
Utilities report lead as a 90th-percentile result from home taps. 1 of 7 San Joaquin County cities reported a value above zero, and none was above the 15 µg/L federal action level. Lead usually comes from a building's own pipes and fixtures, so only a test at your tap tells you what you drink.
Does San Joaquin County have hard water?
Hardness is published in utility water-quality reports for 1 San Joaquin County city on record; the hardest is Stockton at 8.6 grains per gallon. Hardness affects scale and appliances; it is not a health finding.
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